NYC nanny suspected of murdering children raises questions about how families, agencies evaluate childcare providers

(CBS/AP) NEW YORK - The stabbing deaths of Leo and Lucia Krim, two New York City children who police suspect were murdered by their nanny on Thursday, raise questions about how families can adequately assess the person they trust to help care for their children.

PICTURES: Nanny suspected in fatal stabbings of 2 NYC kids

According to Joan Friedman, owner of A Choice Nanny agency, there is a "big range" when it comes to how agencies and families background a potential nanny.

At A Choice Nanny, Friedman says the application process includes multiple interviews, reference checks, and the completion of a detailed questionnaire. This is where the applicant must answer hypothetical questions about how they would handle various scenarios involving children.

In addition, A Choice Nanny, which has offices in Florida, New Jersey, Maryland and New York, runs a criminal background check, a credit check, and a check of the sex offender registry. They also look into a potential nanny's educational background and driving record.

Friedman says that the agency also asks applicants to provide a letter from a doctor showing they are in good health, but that "it's not standard practice" for the agency to look into an applicant's mental health history.

"We're not psychiatrists," Friedman says, and any investigation into a potential nanny's mental health record would be "up to the family."

But according to Susan Tokayer, co-president of the International Nanny Association, employment laws prohibit asking a potential employee whether they have suffered from mental illness in the past.

Tokayer suggests that parents whose children are cared for by a nanny ask neighbors, doormen and playground friends to alert them if they see the nanny behaving in a way that seems odd or inappropriate.

"Sometimes parents aren't around the caregiver as much as other people are," says Toyaker, and letting people know that you want them to be observant can be helpful.

Yoselyn Ortega, the 50-year-old nanny who police suspect killed the two Krim children has not yet been charged in their deaths. After the children's mother, Marina Krim, arrived home and found the 2-and-6-year olds dead in the bathtub, Ortega was arrested and taken to a nearby hospital for treatment of what police believe were self-inflicted stab wounds. She is in critical condition.

According to Marina Krim's blog - which has since been taken down - the Krim family had recently visited Ortega's family in the Dominican Republic. 

Fernando Mercado, the superintendent of the building where Ortega lives, told The Wall Street Journal that she is "a very nice woman" and "very religious."

"To me, she has always been very, very stable," he said.